Tools/programs you recommend for calculating monthly rental estimates?

[Jacob Lopez]

Hello once again BP Community! 

I have been diligently reading, studying, and beginning to practice analyzing cash flows of properties within Chicago and some Chi suburban areas.

While I try to use whatever tools I have at my disposal and also be conservative with my numbers while analyzing properties (vacancy percentage, expenses, etc) I believe that in some areas of my analyses, I may not be getting the most accurate information.

For everyone out there, where do you get your rental estimates by location? I currently use the US Dept of Housing for rent by zip code. 

Thanks !